There are various and sundry means of generating oxygen species ions. These involve arc discharge through the air. An early discourse on such discharge phenomenon is found in the text, “The Discharge of Electricity Through Gases,” Charles Scribner's Sons, New York: 1899. S. S. Thompson, “Lord Kelvin.” Another text is “Fundamental Processes of Electrical Discharge in Gases,” Leob, Leonard, B., John Wiley and Sons, 1939.
A more recent text, “Spark Discharge” by Bazelyan et al; explains the phenomenon of streamers quite nicely. The problem in discharging electricity through air is that air is stubborn. It takes energy to start the arc which results in a type of avalanche breakdown. This avalanche breakdown produces as arc in which electrons have a lot of energy. This is undesirable because these electrons can cleave molecular oxygen, O2, in half to produce atomic oxygen, O. This atomic oxygen can then react with molecular oxygen to produce ozone. Ozone is unwanted because of its proposed harmful effects to humans.
The proposed invention liberates electrons into the air at a low energy. Avalanche dielectric breakdown of the air is absent. The superoxide ion is formed in abundance as opposed to ozone.
Techniques of producing ions in air usually involve a sharp needlelike electrode. At the tip of such a needle the electric field gets very high and dielectric breakdown occurs. These needles can be coated with platinum and gently pulsed to limit ozone production. As a result, superoxide ion generation is also limited. Further, the small surface area of the needle head limits ion production.
Needlelike electrodes in ionization devices are ever present. For pending art see US Patent App. No, 20040025695 to Zhang at al. Therein find discussion of a plurality of wires and ground plates at high voltage to produce dielectric breakdown of the air and thus generate ions. Also is found a discussion of the point ionizer. Both of these techniques involve high voltage exposed to the raw air to produce ions. These devices however also produce ozone. The high voltage arcing through the raw air produces ozone because of the phenomenon of avalanche.
Pulsed corona discharge microwave plasma, and dielectric barrier discharge devices are all reviewed in detail in “Prospects for non-Thermal atmospheric plasmas for pollution abatement”, McAdams, J. Phys. D.: Applied Physics, 34 (2001) 2810-2821.
The pulsed corona discharge and the microwave discharge device involve passing the raw air through the corona and or plasma. This will produce ozone. This is why these devices clean the air, ozone being a powerful oxidant. However, if there are no contaminants in the air the ozone does not get used and itself is a contaminant.
The dielectric barrier discharge device DBD shown in FIG. 1, referring to FIG. 1, find a first electrode, 101, a dielectric barrier, 103, a second electrode, 105, a region between the insulating dielectric barrier and the second electrode where air can pass, 107, and a power supply, 109.
In the dielectric barrier or silent discharge regime, one of the two electrodes has an insulating coating on it and an alternating current (ac) voltage is applied between the electrodes. The microdischarges occur between the insulating surface and the opposing electrode. These microdischarges have a duration of ˜1-10 ns and are self-quenching. They appear as spikes on the current waveform. For a given applied voltage, the capacitances of the insulating layer and the gap between the layer and the opposing electrode together with the applied frequency determine the power dissipation. Such dielectric barrier discharges have formed the basis of commercial ozone generators, with the ozone being used for water treatment for example.
The proposed invention is primarily not a dielectric barrier discharge device. In one of its permutations it has a plasma in an enclosed volume and the barrier is a specific material to execute specific phenomenon. In yet another embodiment the enclosure has its outer surface held at a specific potential to achieve specific results.
The short discharge pulses in region, 107, have a lot of energy and split molecular oxygen in half to the end of producing ozone.
The proposed invention has a specific bias circuit on its outer electrode which when applied to a DBD device can reduce the ozone output of the device and increase its negative ion output. Thus in one of its embodiments it represents an improvement to all DBD devices.
Ion tubes which generate ions and or ozone have been manufactured and used for many years. The bentax tube was reviewed in my earlier U.S. application Ser. No. 10/867,296. Other ion/ozone tubes are disclosed in U.S. Pat. No. 1,793,799 to Hartman (1931), U.S. Pat. No. 1,064,064 to Franklin (1913), U.S. Pat. No. 3,905,920 to Botcharoff, U.S. U.S. Pat. No. 361,923 to Brian (1887). These devices lack the novelties of the proposed invention in that the enclosure of the tube is not specified to be an N-type semiconductor. Also the critical bias potential of the secondary electrode which is present in the proposed invention is absent in these earlier tubes.
Other means of generating negative ions include irradiating a conductor with an ultraviolet lamp to liberate electrons via the photoelectric effect. This method is employed in U.S. Pat. No. 3,128,378 to Allen et. al., U.S. Pat. No. 3,335,272 to Dickinson et. al., and U.S. Pat. No. 3,403,252 to Nagy. The proposed invention does not employ the photoelectric effect not the use of ultraviolet light. The ultraviolet light can produce ozone, O3, as well as atomic oxygen, O, both of which are undesirable.